The failure of a detachable link in an anchor chain caused the decommissioned tanker Monongahela to break free from its mooring during a 2009 norâ€™easter, resulting in $600,000 in damage to the vessel and port facilities in Virginiaâ€™s James River, according to an investigation by the U.S. Maritime Administration (MarAd).
The 700-foot Monongahela, part of MarAdâ€™s â€œghost fleet,â€ moored off Fort Eustis, broke free on the night of Nov. 12, 2009 as the area was hit by the remnants of Hurricane Ida. The ship struck an electrical tower and knocked a transformer into the water, then drifted a half-mile downstream before running aground in thick mud and sand on the western side of the river.
Monongahela, which was removed from military service in 1999 and scheduled for disposal, was refloated on Jan. 27, 2010 by crews from Titan Salvage. The effort involved three 350-ton hydraulic pullers installed on the aft deck of the vessel and nearly 6,000 feet of anchor chain connected to plate anchors in the riverbed upstream. Monongahela was inspected and towed back to the James River Reserve Fleet (JRRF) anchorage the next day.
In assessing the incident, MarAd found deficiencies in equipment and procedures dating to when Monongahelaâ€™s anchors were last handled in 2005. The deficiencies included the use of â€œsubstandard mooring materialâ€ â€” the detachable link that broke â€” and an inadequate mooring configuration due to the lack of a crane with sufficient lifting capacity at the anchorage.
The fleetâ€™s plate anchor system was installed after Hurricane Floyd caused extensive damage to moorings in September 1999. The steel plates were driven into the river bottom a minimum of 125 feet, with vessels moored to the plates with chains. The shipsâ€™ own anchors are also deployed to provide â€œan extra measure of mooring security,â€ according to MarAd.
When Monongahela was repositioned in 2005 following the removal of another ship in the fleet for disposal, the tankerâ€™s 15-ton anchor was not deployed as a backup. Additionally, a section of chain with a detachable link had to be used to make the connection between the shipâ€™s anchor chain and the plate anchor, MarAd said in its investigation report.
â€œThis deviation from normal fleet practice was necessary at that time because a mechanical problem with the fleet crane barge prevented normal anchor and chain handling,â€ the report said. â€œNevertheless, there was little concern with the anchorless arrangement at the time because the holding power of the JRRF plate anchor system was engineered to be sufficient by itself. The typical mooring arrangement of deploying the shipâ€™s anchor alongside the plate anchor connection, however, would have likely prevented the vessel from drifting free.â€
The portion of the parted anchor chain that remained attached to Monongahela revealed that â€œa critical failureâ€ had occurred below the shackle that linked the upper chain to the anchor plate segment, MarAd said. Upon retrieving the remaining section of chain from the river bottom, it was discovered that the detachable link had broken into two pieces.
â€œCompared to fixed links, detachable links are more prone to internal corrosion when submerged over time and tend to break more easily under heavy strain,â€ the report said.
In its report, MarAd said it has made the following changes to improve the security of the James River fleet:
â€¢ The lifting capacity at the anchorage is now maintained at 60 tons, which allows the handling of any anchor and chain.
â€¢ â€œUnderwater moorings are now being periodically inspected and maintained, with critical conditions properly recorded and reported to management.â€
Before the Monongahela incident, fleet policy was not sufficient to allow the detection of problems that could lead to mooring system failure, according to MarAd.
â€¢ The policy will be enforced to ensure that each vessel deploys its own anchor in case the primary mooring fails.
Monongahela sustained two holes in its hull when it struck the fleetâ€™s No. 7 electrical tower, with damage to the ship estimated at $100,000. Damage to the tower and the transformer that was knocked into the river was estimated at $500,000. MarAd also incurred $500,000 in salvage expenses, according to the investigation report.
The tanker is still awaiting disposal.